1. Field of the Invention
This invention relates to a vehicle route guidance apparatus for aurally guiding the user through a route in a voice and more particularly to volume control therefor.
2. Description of the Related Art
Various types of apparatus to relieve drivers of their work load have been designed and are carried by vehicles; one of them is a route guidance apparatus for guiding the user through a route to a destination. A route guidance apparatus which has a function of informing the driver of routing, when the vehicle passes a branch point such as a crossing, for guiding the driver through the route using a generated voice is known.
On the other hand, usually the vehicle is equipped with audiovisual machines such as a radio, television, and cassette tape recorder and is provided with voice output means such as a loudspeaker unit. Thus, it may be preferable that a voice for route guidance is also output from the audio loudspeaker unit. The aural route guidance is disclosed, for example, in Japanese Patent Laid-Open No.Hei 1-173815.
However, an output from audiovisual machines differs entirely from a voice for guiding the driver through a route in nature or purpose. The purpose of the voice guidance is only for the driver to listen to what the guidance says; the audiovisual machines also output music and are often not intended for the user to clearly listen to what the output says. Therefore, it is not preferable that the volume of the guidance voice is set to the same as that of the audiovisual machine output. Ease of listening to the guidance voice varies depending on the in-vehicle environment such as the amount of vehicle running noise and audiovisual machine output; the preferred volume for the guidance voice also varies from one person to another.